Manufacture of hexamethylenetetramine



July l2 1927.

1,635,707 C. B. CARTER MANUFAGTURE or? HExAMETHYENETETa-AMINE Filed Feb. s, 1924 Iz'quz'q! JJ( mozzz'uzv iara'de we.

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Patented Julyiz, 1927. i

UNITEDv` STATES PATENT OFFICE.

CAR-NIE B. CARTER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR To s. KARPEN e EROS., OE CHICAGO, ILLINOIS, A CORPORATION OE WEST VIRGINIA.

MANUFACTRE OF HEXAMETHYJLENTETRAMINE.

Application led February 9, 1924. Serial No. 691,673.

'lhe present invent-ion relates to an improved process which enables hexamet-hylenetetramin-e to be produced easily. quickly, and 'at reduced cost. Hcxamethylenetetramino can be prodpced by reacting on methylene chloride with ammonia under suitable conditions, in accordance with 'the theoretical proportions, as set forth'in the follow- 0 ing equation:

lt has been known for many years that ammonia in solution in alcohol reacts \vitl i methylene chloride: Holand as far back as 1887, testing for carbon affinities, heated theoretical proportions of methylene chloride andammonia in alcohol solution. l-Ie did not complete the reaction, however. and he did not succeed in isolating hexamethylenetetramine, although he stated, in effect` that he obtained a sublimate which possessed the properties of hexamethylene-amine. It. can now be demonstrated that the presence Ot Water. in the Holand experiment, results infaphenomenon of hydrolysis leadingr to the production of hexamethylenetetraminehydrochloride.

Later, Delepine (2), in 1894. produced 3o' hexamethylenetetramine hydrochloride by heating a solution of methylene chloride and ammonia in methyl alcohol; He employed proportions giving rise directly to the production of the hydrochloride, which prod- The equa- .tion given by him is as follows:

1 Liohia's Annalen, 240. 225 (1887). 2Bull. Soc. Chim., (3) 11, 556 (1894).

enetetramine and ammonium chloride, and that the hexamethylenetetramine could be separated from the ammonium chloride in a very simple manner and be. thus obtained directly in aI high state of purity. In lmy application Number 685,456, tiled January .10, 1924, is set forth an improvement on our joint invention mentioned, said improvement. being based upon the discovery that a very large excess of ammonia, preferably an excess of 300% orlmore above the theoretical proportion, would very greatly increase the. reaction velocity and enable the reaction to'be carried out at greatly reduced pressure, using a moderate period of heating. In both these liquid ammonia processes, the phenomenon of hydrolysis does -pot appear or present any obstacle, because water 1s not present, or, 1f present, 1s only present. in very small percentage. Moreover, in those processes, ammonia is presentin the liquid form to al certain extent in the products of the reaction and will thus operate to prevent hydrolysis if a. small proportion of Water be present.

The present invention is based upon four discoveries, viz:

l. That the presence of Water in a reaction mixture of methylene chloride and ammonia greatly increases the reaction velocity.

2. That the phenomenon of hydrolysis, with consequent production of hexamethylenetetramine hydrochloride, may be obviated by maintaining an excess of ammonia while Water is present in the reaction mixture Or in the resultant mixture of compouirds so .that it will be impossible for hydrochloric acid to form as a result of the reduction of ammonia below the theoretical proportion at any time, or in any portion of the mixture.

3. That the use of a large excess of ammonia in aqueous solution greatly expedites the reaction and enables the process .to be carried out at lower pressures and in less time than is possible by the use o the liquid ammonia process emp oying a large excess of ammonia.

4. 'Ihat alcohol is not required as a solvent for the methylene chloride, since ammonia in aqueous solution serves this function; and that alcohol acts to retard the reaction, and, if used in'very high percentage, will so decrease the reaction velocity-as to render the The following experiment illustrates the retarding action of alcohol and the effect of the phenomenon of hydrolysis as the result till of water present in commercial alcohol used as a solvent:

A glass test tube having a capacity of 25 to 30 cc. was prepared for the experiment. '.lhis tube which Was hermetically sealed con tained 2.56 gramsof methylene chloride and 9.8 cc. of (commercial) alcoholic ammonia solution. Analysis of the alcoholic ammonia solution, prepared by dissolving dry ammonia gas in alcohol, showed that the tube carried (some excess) 1.60 grams of ammonia as against a theoretical requirewearer ment ot 1.37 grams. The tube was heated in boiling water for a period of 72 hours after which the contents were transferred to a small flask and the alcohol distilled oil' on the Water bath. The residue from the evaporation was extracted' with pure dry chloroform to remove all hexamethylcnetetramine and leave the ammonium chloride. lvlexainethylenetetramine was recovered from the chloroform and weighed. lThe ammonium chloride was determined by analysis.

llexamethylcnetetramine recovered, 0.180 gram, equivalent to 0.60 gram of methylene chloride. Chloride l'ound calculated as methylene chloride 1.16 grams.

Tlieresult-s show two facts very clearly. ln the first place they show that the reaction is only 45.3%k complete after 72 hours of heating at G C., 1n the second place, they show that only 59.5% of the theoretical yield of hexamethylenetetramine is obtained. The chloride present in the reaction product shows that 1.16 grams of methylene chloride has reacted: accordingly there should be produced 0.318 grams of hexamethylenetetramine, whereas only 0.189 gram is actually recovered. The poor 'hexamethylenetetramine yield is due to Water in the alcohol. The effectiveness of Water in diminishing the hexamethylenetetramine yield is still more strikingly shown by the following experiment:

similar test employing a solvent con- Sistiner of 85% alcohol and 15% Water with a slightly decreased percentage of ammonia, which, however, Was still slightly above the theoretical percentage showed, after 72 hours heating at 100o C., a reaction 64.1% complete and a yield of 22.4% of the theoretical yield at this stage.

In the experiments just mentioned, doubtless, hexamethylenetetramine was actually produced in theoretical quantity and was .y contained in solution as such in the liquor.

In the evaporation process, however, a slight excess of ammonia escaped and this was followed by escape of ammonia' involved in the phenomenon of hydrolysis, so that hydrochloric acid remained in the liquor, thus forming the hydrochloride. The phenomenon of hydrolysis will be understood by consideration of the following equations which may be considered as representingreactions which `take place in the reacting mixture when ammonia is not present y in large enough proportion to prevent an unbalancing.,T etlect as the result of the escape of animonia:

(ci-named enzo l The followingr experiments illustrate the loss from hydrolysis, and the method ol' overcoming the loss:

Two mixtures were prepared, each containing 0.3 gram of pure hexamethylcnetetramine and 1.4 `grams of pure ammonium chloride (essentially the proportions in which these products would he formed in the reaction) dissolved in 25 cc. of 85% alcohol.

Mixture No. 1 Was placed in a flask on the Water bath and the solvent distilled oil" as completely as possible at 100 ("f. The residue was hygroscopic and gummy due to the hygroscoplc character of hexainethylene- `tetramine hydrochloride.

llll

.noemer whereas thelack of ammonia in the evaporation has resulted-in the loss of more than 80% of ythe hexa. g The term loss is not used in the absolute sense; most of the hexamethylenetetramine still exists in the residue in the form ofpits hydrochloride and may be converted' into free hexamethylenetetramine by treatmenty with ammonia gas. Some loss by escape, however does occur, due to hydrolysis of hexamethylenetetramine in the presence of hexamethylenetetramine hydrochloride, andthe evolution of free formaldehyde together with the solvent. It is necessary, therefore, to maintain an excess of ammonia at all times in the evaporation and drying in order to prevent this loss. Several methods of handling this problem of hydrolysis are applicable, butl further discussion of this subject will be deferred until after 'the reaction velocity has been discussed.

The reaction takes place in alcoholic solutions, both aqueous alcoholic and absolute alcoholic solutions, and also in aqueous solution. The reaction proceeds with the greatest. ease and most rapidly in pure aqueous solution and with increaslng sluggishness as P the alcoholic content increases. These facts y were established by a series of five experilit) ments, each employing five test tubes. The manipulative procedure was as follows in all experlments: Small glass tubes Wereprepared and hermetically sealed; each tube containing 0.170 gram of methylene chloride and 2.1 cc. of alcoholic ammonia` solution. The alcoholic content varied from 25% to 100% and the ammonia content was maintained approximately constant at 35% excess ammonial over and above that required theoretically for the methylene chloride used. All tubes were heated in boiling water and their contents-analyzed for chloride in order to establish the ,state of the reaction. The following tables show the first and fifth of these experiments, and the intermediate experiments will be commented on briefly:

Reaction velocity in absolute alcohol at a temperature of 100o C.

Experiment Z.

Heated. State of reaction.

0.5% complete. 10. complete.

23 0% complete.

5% complete.

151 hours 68.0% complete.

Emperimenf 5.

Tube. Heated. State of reaction.

l 1.5 hours 9.0% complete.

67.5% complete. 85.0% complete. 93.0% complete. 98.9% complete.

hours, and was 98.4%

, By experiments of an intermediate character, it was found that, employing a solvent consisting of 95% alcohol and 5% water, the results did not vary to any notable extent Afrom the results obtained in Experiment 1;

Dealing with a solvent consisting of 85% -alcohol and 15% water,the reaction was Reaction in aqueous solution.

The hexamethylenetetramine reaction takes place readily inaqueous ammonia solution and more' particularly in solutions'of high ammonia concentration. These facts are clearly shown inthe following series of exeriments:

Five test tubes were prepared and hermetically sealed, each containing 0.170 gram of methylene chloride and 2.1 cc. of aqueous ammonia solution, of the ammonia content listed below. All tubes were heated in boiling water at the same time for a period of four hours and the state of the reaction with respect to the contents ofeach tube isset forth in the table:

The foregoing shows that the' ammonia concentration is of quite considerable imortance in governing the reaction velocity. t may be added that the concentration in tube 5 is somewhat less than the concentration of ordinary commercial aqueous ammonia (27% to 28% strength).

Temperature is alsoa factor governing the reaction velocity. Reaction takes place in aqueous ammoniay solutions even at ordinary atmospheric temperatures, but with very low reaction velocity. The reaction Velocity has not been followed out fully at room temperatureLbut it can be stated that reaction is only 2% to 3% complete at 20 to 25 C., after 150 hours. The reaction velocity .increases rapidly and becomes of practical importance at temperatures, say, ranging from 50 C. to 120o C. For example, employing aqueous ammonia solution in about 400% excess above the theoretical quantity, the reaction can be completed at a temperature of in about 150 hours, can be completed at llO 100 C. in about 9 hours, and can be completed at 120 C. in about 3 hours. .Practical considerations will govern the temperature to be employed in a Working plant. AV

preferred range of temperature is somewhere between C. and 120 C., and perhaps, for all around purposes, about C. is the best temperature to employ.

The following may be given as an example of the improved method:

Introduce mto an autoclave methylene chloride and an aqueous solution of ammonia, employing a concentration of ammonia which preferably is a saturated solution, or nearly so, at room temperature; take a Suthcicnt quantity of aqueous solution of ammonia to give an excess of 300 or 400% of ammonia above the theoretical proportion as explained in the first equation given above. lolcat the autoclave at a temperature in the neighborhood of 100 C. until the reaction is complete. that is, until all of the methylene chloride has reacted. Ordinarily, this will require a period of eight to ten hours. As the temperature in the autoclave rises, the pressure rises from approximately atmos pheric pressure to perhaps 10U-to 125 pounds, depending' upon the rate of heat, for it is to bei observed that while the pressure is a function of the temperature, the pressure is also affected by the consumption of the reagents during the reaction, the pressure tending to fall as a result of the reaction.

'lhe time may be shortened greatly by increasing the temperature to 120o C. and the resultant pressure will be somewhat higher, say, a maximum in the neighborhood of 150 pounds per square inch.

The amount of methylene chloride irst introduced int-o the autoclave may be sulicient to produce substantial saturation of the liquor with hexamethylenetetramine and ammonium chloride at the completion of the operation, and fresh ammonia may be pumped into the autoclave, from time to time, as the heating is continued, to maintain the desired excess-percentage of ammonia. After the reaction has been completed, the liquor, containing the hexamethyleneletramine and ammonium chloride produced by the reaction, is withdrawn from the autoclave. The products of reaction may be separated from each other by any suitable method, care being taken to avoid conditions which might produce the phenomenon of hydrolysis. One method of procedure is to evaporate the solvent under such conditions as to maintain free ammonia in contact with the reaction products at all times. Thus, for example, the evaporation of Water and ammonia may proceed, employing suitable facilities to recover the ammonia driven otl; and before all of the free ammonia escapes, to introduce a stream of ammonia gas into or through the products of the reaction Lesmo? and maintain an ammoniacal atmosphere during the drying of the residue. After the residue has been properlydried, it may be subjected to the action of a solvent which will dissolve the hexamethylenetetramine, Without dissolving the ammonium chloride. The lhexarnethylenetetramine may then be recovered from the solvent. Any Suitable solvent, such as chloroform or carbon tetrachloride may be employed.

Another method of effecting separation is to remove the solvent under reduced temperature and pressure, that is by employing a vacuum process and removing solvent or water to a point where the reaction products remain as a gununy mass; then introducing a stream of ammonia to produce an ammoniacal atmosphere and drying either at low or elevated temperature. The drying can be carried out either under partial vacuum, or at atmospheric pressure, if the precaution be taken to maintain an ammoniacal atmosphere in Contact with the products of reaction. The selniration of the hcxametliyleuctetraniine may then be effected in any suitable manner.

lVhere the process is to be practiced on a commercial basis, an elaboration of the process probably is desirable. rlhe accompany ing drawing illustrates, diagrammatically, apparatus, or a How sheet ot' apparatus, for practicing such process, and the process will be described in connection therewith.

In the drawing, A represents a storage tank ivhich may be regarded as containing a supply of solution of ammonia, preferably a concentrated solution, saturated with hexamethylenetetramine and ammonium chlo ride; B, an autoclave which connnunicalcs, through a pipe 1, with the storage tank A; C, a storage tank containing methylene chlo` ride, and which communicates, through a pipe 2, With the autoclave; D, a cooling-tank which will serve to cause the ammonium chloride formed in the reaction to be deposited or crystallized out. and which may serve also to receive an additional supply of a1nmonia to cause the hexamethylenetetramine formed in the reaction to crystallize out, the cooling-tank D communicating with the autoclave, through a pipe 3, and heilig equipped with a cooling jacket served by water-circulating pipes 4; E, a filter or centrifuge adapted to receive the contents of the tank B, through a pipe 5, the liquor from the device E being adapted to ret-urn to the tank A, through a' pipe 6; F,'a drier adapted to receive the ammonium chloride and hexamethylenetetramine from the tank E, through a pipe 7; G, an extractor, or tank, adapted to receive the dried products from the drier F, through a. pipe 8; H, a solvent-storage tank, which may contain chloroform, for example, said tank communicating with the extractor, through a pipe Y9; I, a still which receives the solution of hexamethylenetetramine from the extractor G, through a pipe 10; J, a storage tank for hexaniethylenetetramine which receives the hexaniethylenetetraminc from the still I, through a pipe ll; K, a drier which receives the ammonium chloride from the extractor G, through a pipe 12; li, a storage tank for the ammonium chloride; M, a storage tank t'or liquid ammonia from which extends a supply pipe 13, equipped with a reducing valve 14; 15, a branch pipe connecting the pipe 13 below the reducing valve with the cooling. and crystallizing tank I); 16, a pipe forming an extension ot' the pipe 13 and connected with the drier F; and N, a condenser which receives solvent vapors from the drier F, through a pipe 17, and which, in turn, communicates, through a pipe 18, With the pipe 13 below the reducing valve 14.

The system is shown further equipped with valves l19, 20,21, and 22.

ln operatingV the system, a suitable supply of what may be termed the stock liquor is taken from the tank A into the autoclave B. From the tankC, the desired amount of methylene chloride is admitted to the autoclave. Preferably the amount ot methylene chloride admitted is such as to constitute about 20% of the theoretical amount required to combine with the ammonia contained in the stock liquor in the autoclave. The autoclave is heated Jfor a sul'l'icient length otl time to cause reaction of the methylene chloridevtherein; the liquor is then withdrawn through 4the cooling and crystallizing tank l) and is there cooled preferably7 to about room temperature; ammonia is then admitted. through the pipe 15, which is controlled by a valve 15, and the cooling is continued to compensate for the heat ot' solution of the ammonia. The effect ot the cooling is to crystallize out the ammonium chloride-formed by the reaction in the autoclave; and the etect of introducing ammonia through the pipe 15 is to crystallize out the hexamethylenetetranline formed in the reaction and restore the stock solution content to its original percentage in the stock liquor. From the device D, the liquor containing the precipitated products ot reaction passes to the filter or centrifuge E and from there the mother liquor is returned, through the pipe 6, to the stock liquor tank A.. The admission of the solvent from the tank H to the extractor G is controlled by a valve 91.- Other valves may be added to the system, if desired. It should be understood, of course, that the drawing represents a ioW sheet, and Where pipes have been mentioned, they may not bc used in actual practice in some instances. For example, it the device E be a centrifuge, the products of reaction from which the mother liquor has been driven by centrifugal action will be removed by any suitable mechanical means fromythe centrifuge to the drier F.

It Will be noted, fin considering the foregoing method that ammonia passes through the pipe t6 to the drier' i", while the remaining amount of solvent is being evaporated from the reaction products. rlhis precaution is taken notwithstanding the fact that the mother liquor contains a large excess,

percentage of ammonia, the purpose heilig to constantly supply ammonia to replace that which is driven ol'l in the drying operation.

rl`he crystallizing of the hexamethylenetetramine by the introduction ot ammonia into the crystallizer l) depends upon the phenomenon that an increase in ammonia content of the liquor decreases the ability ot' the liquor to serve as a solvent for the hex` amethylenetetramine. the hexamethylenetetramine goes into` or is Jformed in solution` in the autoclave B, due to a reduction in the ammonia content re.- sulting from the reaction, it being borne in mind that at the start the liquor being heated in the autoclave is saturated with hexamethylenetetramine. Again, an increase in ammonia content in the stock liquor On the other hand,-

increases to a certain extent the ability ot the liquor to dissolve ammonium chloride. This last phenomenon is of no particular consequence in the method carried out here described, however.

From explanations given above. it will be understood that the reaction may be eli'ected in the autoclave, regardless of whether an excess ot' ammonia is employed or not., provided there is sufficient ammonia present. in

the autoclave at all times to correspond with the theoretical proportion. Practically speaking, this means that some excess oi am` monia must be present. in order that no phenomenon of hydrolysis may occur. l`he effeet of the use of a large excess of ammonia in the autoclave is to greatly expedite the reaction. ()n the other hand, when the drying is effected in the processes here described.A

it is essential to'maintain an ammoniacal atmosphere while the drying is heilig done.

The improved process provides for producing hexamethylenetetramine directly from methylene chloride and ammonia in 'a simple and economical manner, and possesses important advantages over known methods.

Any suitable source of supply for ammonia may be used. Preferably the source of supply is a tank of liquid ammonia.

It will be understood that by employing in the system a stock liquor saturated with hexamethylenetetramine and ammonium chloride, it is possible to crystallize out the hexamethylenetetramine and ammonium chloride which are formed in the reaction and avoid evaporation of the solvent, except for the traces which remain after the cen- Elli elli

trii'nge operation. While, tor the purpose oit illustration, the tank A has been assumed toy be provided With a stock liquor enabling the operation to be started on the right oasis from the outset, nevertheless, it is understood that it is quite possible to build up the liquor to a point Where it is saturated with henamethylenetetramine and ammonium chloride by supplying requisite quantities ot methylene chloride and gaseous ammonia until the point of saturation is reached, that is, avoiding the emptying ot the autoclave until the liquor has been built up to this strength. rthe system may then be operated in the manner explained.

llrom the enplanation viven above, it iollows that in operating tie process advantageously, rather a Wide latitude is allowable in the' proportionl ot the methylene chloride employed with respect to the ammonium employed in the reacting mixture. rlfhus, operating the system employing the aqueous solution saturated with heramethylenetetramine and ammonium chloride, the proportion of methylene chloride employed .may vary through a range et trom to el the theoretical amount required to combine With the ammonia present in the reacting mixture, and still the operation may be carried out Within a reasonable period ot time.

'lhe foregoing detailed description has been. given tor clearness ot understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in View of the prior art and in view ost the premises.

lli/That l regard as new and desire to secure by luetters Patent is:

l. rlthe process ol producing hcnamethyl` enetetramine which comprises: reacting upon methylene chloride with ammonia present as a constituent et a solvent composed largely of Water.

- lhe process or producing heii'amethylenetetramme Which comprises: reacting upon methylene chloride with ammonia present as a constituent oi a solvent eomposed largely ot' Water, the ammonia being present in eiicess ot the theoretical proportion.

3. 'lheprocess of producing. heiramethylenetetramine which comprises: reacting upon methylene chloride with ammonia present as a constituent ot a solvent com-- posed largely of Water, the ammonia bein` present in proportion corresponding Witii more than one hundred per cent excess above the theoretical proportion.

Li. rlhe process of producing heiramethylenetetramine which comprises: reacting upon methylene chloride With ammonia present as a constituent of a solvent containing Water, and electing drying While maininsurer taining in contact With ammoniacal atmosphere said ,reaction products.

The process of producing hexamethyl enetetramine which. comprises: reacting upon methylene chloride with ammonia present as a constituent ol a solvent composed largely oi' Water, the reacting mixture being heated to a temperature above 50 C.

6. 'lhe process of producing hexamethyly enetetramine which comprises: reacting upon methylene chloride with ammonia present as a constituent olf asolvent composed largely of Water, the ammonia being present in a proportion corresponding with an excess ot more than one hundred per cent above the theoretical proportion and the reacting mixture being heated to a temperature above 50 C.

'lhe process ot producing henamethylenetetramine which comprises: reacting upon methylene chloride with ammonia in a, liquor comprising aqueous ammonia substantially saturated with heiramethylenetetramine and ammonium chloride, the proportion o'l methylene chloride employed in the reaction being less than the theoretical pro portion required to react with the ammonia. present in the reacting miirture. y

il. 'lhe process oi producing heiran'iethylenetetramine which comprises: reacting upon methylene chloride with ammonia. in a liquor comprising aqueous ammonia, substantially saturate(` with hea'amethylenetetrainineand ammonium chloride, the proportion of methylene chloride employed in the reaction being lessthan the theoretical proportion required to react with the ammonia present in the reacting mixture, the reacting mixture being subjected to a temperature above 50O C. y

9. rlhe process ol producing henamethylenetetramine which comprises: reacting tlti upon methylene chloride with ammonia in,

a liquor comprising aqueous ammonia substantially saturated with henamethylenetetramine and ammonium chloride, the proportion of methylene chloride employed in the reaction being less than the theoretical proportion required to react with the ammonia present in the reacting mixture, the reacting mineure being subjected to a temperature above 50 C., and then e'ecting separation from the liquor of the products pr0- duced by the reaction.

10. rlhe process ot producing hexamethyl-` enetetramine which comprises: reacting upon methylene chloride with ammonia in a liquor comprising aqueous ammonia substantially saturated With ammonium chloride and hexamethylenetetramine, the methV ylene chloride being present in the reacting mixture in a proportion corresponding with substantially less than the theoretical proportion and the reacting mixture being sub-` jected to a temperature exceeding 50 C.,

`with all the ammonia.. present in the reacting mixture. Y

12. The process of producing hexamethylenete'tramine which comprises reactin upon methylene chloride with ammonia present as a constituent oa solvent composed largely of water, separating the products of reaction from the bulk of the',

solvent, and effecting'drying `of the produts of reaction YWhile maintaining the same ilhrgontact with an ammoniaca] atmosphere. "L13,l The' process of producing hexamethylenetetramine which comprises: reacting upon methylene chloride with ammonia present as a constituent of a. solvent composed largely of water, separating the products of reaction from the bulk of the solvent, and -separating the hexamethylenetetramine formed in the reaction from the ammonium chloride formed in the reaction.

14. The process of producing hexamethylenetetramine which comprises: reacting upon n'iethylene chloride with ammonia in a liquor comprising aqueous ammonia substantially saturated with liexamethylenetetramine and ammonium chloride, the r0- portion of methylene chloride'employe in the reaction being less than the theoretical proportion required to react with the amtion, separating the bulk monia present in the' reacting mixture, crystallizng out from the llquor products formed in the reaction, drying the products of reaction in an ammoniacal atmosphere, and separatin the products of the reaction from each ot er.

15. The process yof producing hexamethylenete'tramine which comprises: reacting upon methylene chloride with ammonia present as a'constituent of a solvent composed largely of water, the ammonia being present in a proportion exceeding the theo-- retical proportion and the reaction mixture being heated to a temperature above' 50 C. While being maintained under pressure, separating the reaction products from the liquor, and drying the reaction products in an ammoniacal atmosphere. z"

16. The process of producing hexamethylenetetramine which comprises: reacting;

upon methylene chloride with ammonia in a solvent comprising aqueous ammonia substantially saturated with hexamethylenetetramine and ammonium chloride, the proportion of methylene chloride :,wbeing less thanA the theoretical proportion required to react with the ammonia present in .the reacting mixture, the reacting mixture being subjected to a temperatureexceeding i C., while being maintained under pressure, cooling the liquor after completionv of the reaction to crystalli'ze out the ammonium chloride formed, introducing ammonia into the liquor to substantially restore the'proportion of ammonia and crystallize out the hexamethylenetetramine formed in thereacof the liquor from the products ofraction, drying the products in an ammoniaca] atmosphere, and extracting the hexamethylenetetramine from the ammonium chloride formed in the reaction.

CARNIE CARTER. 

